Solution
Target Common Attenuation is related to the RFSG output power. It can be set to a maximum of 0, and all target attenuations are applied digitally unless a Ranger Rick (NI-5699) is in the system. It does not directly alter RTG Fixed Analog Attenuation.
The purpose of Target Common Attenuation is to optimize the RFSG output power level in both analog and digital domains. For instance, if all targets are around 0dBm, setting common attenuation to 0 and using digital gain helps maintain dynamic range. However, if targets are at -40dBm, setting common attenuation to 0 would not optimize the output power, and adjusting it to 40dBm would maintain a high dynamic range. Ranger Rick (NI-5699) helps dynamically adjust RF analog output power and minimize digital corrections. External Attenuation focuses on system-level gains/losses not accounted for in RTG calibration, aiming for close to 0 dB system loss.
The default value provides an RTG max output power level up to 0 based on the RF calibration path. If there are system losses greater than the max output power the RTG VST can provide, the Common Attenuation value will increase, such as when adding a 20 dB attenuator.
RTG Calibration is done at discrete steps, so the values are coerced to the nearest calibrated power level. For example, entering 0 dB, 1 dB, and 2 dB might automatically update to 0.22 dB, 0.73 dB, and 1.84 dB, respectively.